Background: This study aimed to evaluate the neutrophil-lymphocyte (NLR) and platelet-lymphocyte (PLR) ratios as markers of perforated appendicitis. Methods: We conducted a cross-sectional analytical study. We performed a secondary analysis of a population of pediatric patients who underwent appendectomy between 2017 and 2019 at the Regional Hospital of Ayacucho, Peru. Logistic regression models were used to analyze markers (NLR and PLR) and perforated appendicitis. Later, ROC (receiver operating characteristic) curves were constructed, and sensitivity, specificity, and likelihood ratios were estimated. Results: We identified 31% of perforated appendicitis in 203 patients. A significant association was observed between perforated appendicitis and NLR values > 10.4 (odds ratio [OR]: 2.53; 95% confidence interval [95% CI]: 1.27-5.05) and PLR > 284 (OR: 2.11; 95% CI: 1.09-4.08) in the adjusted analysis. For these models, the areas under the curve were 0.74 (95% CI: 0.67-0.81) for both variables. With a cut-off point of 30% probability of perforated appendicitis, we observed sensitivity of 77.78% for both NLR and PLR (likelihood ratio +2.37 and +2.14, respectively), and specificity of 67.14% and 63.57% for NLR and PLR (likelihood ratio −0.33), respectively. Conclusions: Our study showed a significant association between NLR and PLR and acute perforated appendicitis. Future studies should validate the model and corroborate the performance of these markers.